POSTGRADUATE STUDIES

Buchet Victor, 2014

Title: Impact assessment of invasive flora species in Posidonia oceanica meadows on fish assemblage: an influence on local fisheries? The case study of Lipsi Island, Greece.

Univerisity: University Centre of the Westfjords. Suðurgata 12, 400, Ísafjörður, Iceland

Committee:  M. Honeth, Z. I. Konstantinou, D. Arnarsdóttir

Summary: Seagrasses are one of the most valuable coastal ecosystems with regards to biodiversity and ecological services, whose diminishing presence plays a significant role in the availability of resources for local communities and human well-being. At the same time, Invasive Alien Species (IAS) are considered as one of the biggest threats to marine worldwide biodiversity. In the Mediterranean, the issue of IAS is one which merits immediate attention; where habitat alteration caused by the human-mediated arrival of new species is a common concern. Indeed the Mediterranean Sea is considered to be one of the main hotspots of marine bio-invasions on earth. In this context, the present study examines the possible impacts of flora Invasive Alien Species on the fish assemblages associated with Posidonia oceanica seagrass habitat, and the possible impacts that any change might have on local fisheries. The setting for this study is Lipsi Island, in the Dodecanese, Greece. *In situ*, Underwater Visual Census’s (UVC) were carried out at 14 sampling sites. Fish community parameters were estimated across three substrate types: dense P. oceanica, sparse P. oceanica and sparse invaded (by IAS flora) P. oceanica. External factors and percentage of flora cover were estimated for each substrate. Two flora IAS were found: Halophila stipulacea, one of the first species introduced in the region, which arrived after the Suez Canal opening (also known as a Lessepsian migrant), and Caulerpa cylindracea, a recent introduction through an unknown vector. The present study on the finfish assemblage around Lipsi Island supports the findings of similar studies undertaken in the Mediterranean. The results of the present study show that a low percentage of IAS does not have a significant impact on the finfish assemblage and thus does not seem to have had a significant impact on the local artisanal fishery. With little previous work in the region and no previous work on the Island, this study provides a baseline for future evaluation of changes produced by IAS and for potential management actions such as the creation of marine protected areas in the study region.


Tsiamis Kostas, 2012

Title: Alien macroalgae of the sub-littoral zone of the Greek coasts.

University: Athens University, Biology Department, Section of Ecology and Systematics, Panepistimiopolis 15784, Athens, Greece

Committee: A. Economou-Amilli, C. Katsaros, P. Panayotidis

Scope: Contribution to the study of alien marine benthic macroalgae (Chlorophyta, Fucophyceae, Rhodophyta) in the sub-littoral zone of the Greek coasts, mainly focusing in their presence, abundance, distribution and spread. Studied sites: N. Aegean Sea (Themaikos Gulf, Sithonia Chalkidiki, Pagasitikos Gulf) S. Aegean Sea (Saronikos Gulf, Andros Island, Milos Island, Rhodes Island) and Ionian Sea (Messiniakos Gulf, Leukada Island, Zakinthos Island, Parga – West coasts). Special interested in invasive species: Caulerpa racemosa var. cylindracea, Asparagopsis taxiformis, Stypopodium schimperi, Codium fragile spp. tomentosoides, Womersleyella setacea; monitoring their spread since 2003. In addition: study of aliens’ behavior and impact to the native vegetation; vulnerability of benthic communities to aliens introduction, especially in cases of harbors and stressed ecosystems.


Kalogirou Stefanos, 2011

Title: Alien Fish species in the Eastern Mediterranean Sea: Invasion Biology in Coastal Ecosystems

University: University of Gothenburg. Faculty of Science, Department of Marine Ecology, Kristineberg Marine Research Center, Kristineberg 566, 450 34 Fiskebackskil

Committee: Prof. Magnus Appelberg, Prof. Rosengren, Docent Johan Hojesjo

Supervisors: Prof. Leif Pihl, Assoc. Prof. Hakan Wennhage
Examiner: Prof. Kristina Sundback
Opponent: Dr. Daniel Golani
External mentors: Maria Corsini-Foka, Dr. Andreas Sioulas

Scope: The objective of the proposed research is to study the impact of certain IAS on native and economically important species in a specific area and their role as predators and competitors.

Abstract: The spread of non-indigenous species (NIS) in the eastern Mediterranean Sea is an ongoing and accelerating process. Non-indigenous species are regularly reported from various coastal habitats in the eastern Mediterranean Sea but findamental knowledge on the assemblage structure of coastal fish communities are lacking. This thesis aims to increase the knowledge on the fish assemblage structure and function of Posidonia oceanica meadows and sandy habitats in a coastal area of the eastern Mediterranean Sea and give insight into invasion biology by investigating the potential impact of introduced fish species to the local ecology and food-web of the marine systems under study. Functional and feeding guilds were developed to investigate the fish assemblage structure and function of coastal fish communities and to assess the potential role of NIS in the food web. In addition, diet investigations were considered important first steps in order to evaluate the potential role and impact of recently established NIS in the recipient region. During the sampling campaign two species were for the first time reported in the area. Posidonia oceanica was found to be a multifunctional habitat for fish species. It was found to be a highly important nursery habitat for several species during summer and a habitat that could under certain seasons concurrently be used by both adults and juveniles. Four functional guilds were created to describe the habitat use of P. oceanica meadows for each species encountered, juvenile migrants, seagrass residents, seasonal migrants and occasional visitors. Affinity of each speies to P. oceanica was assessed in a comparison with each species distribution on open sand within the same depth range. Among the 88 species encountered, eleven were found to be non-indigenous of Indo-Pacific and Red Sea origin, three of them using seagrass mainly as juveniles, and four as residents. In a comparison of fish assemblage structure between seagrass and sandy habitats quantitative sampling in combination with classification of species into six major feeding guilds revealed the position and contribution of non-indigenous species (NIS) in the food web of Posidonia oceanica and sandy habitats In P. oceanica beds and on sandy bottoms 10 and five species, respectively, were non-indigenous of Indo-Pacific and Red Sea origin. The proportional contribution if NIS individuals on P. oceanica beds was lower than that of sandy bottoms (12.7 vs. 20.4%) a pattern that also followed for biomass (13.6 vs. 23.4%) indicating that low diverse systems may be more prone to introductions than species-rich communities. The two habitats had similar fish feeding guilds, but the biomass contribution from NIS varied within each guild, indicating different degrees of impact on the available resources. Size was considered highly important due to habitat shift of  species with increased size. Two of the aspects considered in this study, the chance of establishing and the chance of being very dominant will depend upon competitive abilities strongly coupled to size and grounds for habitat shift. However, success of establishment will also depend on appropriate food resources in the recipient community as well as competitive abilities and level of competition in the food web within habitats. No support could be found for the theory that taxonomic affiliation could facilitate invasion success. The non-indigenous bluespotted cornetfish Fistularia commersonii was found to be a strictly piscivore predator and the diet consisted of 96 % by number and >99 % by weight of fish. The diet of F. commersonii was related to time of year, and fish size. Size classification and habitat of prey groups (benthic, supra-benthic, and pelagic) showed that with increased body length it extended its diet to larger prey and more generalist feeding. Fistularia commersonii was found to prey on commercial important native species (e.g. Spicara smaris, Boops boops, Mullus surmuletus) and the absence of NIS from its diet was mainly attributed to the absence of NIS with elongated body shape. The feeding ecology of two common indigenous (Sphyraena sphyraena and Sphyraena viridensis) and one abundant non-indigenous barracuda,Sphyraena chrysotaenia, of Indo-Pacific origin, was investigated. Confamilial feeding interactions was studied to investigate overlap in feeding preferences in relation to availability of prey items. Dietary analyses revealed that all three species examined were specialized piscivores with their diet consisting to more than 90 % of fish, both by number and weight. All three predators examined showed a significant selectivity towards Atherina hepsetus. Diet breadth and size of prey increased with increased body size, whereas diet overlap between indigenous and NIS decreased, attributed to increased diet breadth and specific life characteristics of indigenous species developing into larger predators extending their foraging habits. During winter, condition of the NIS was significantly lower than that of the indigenous species, indicating that winter temperature in the studied area may be a limiting factor for further population growth of this Indo-Pacific species. This study filled the gap in knowledge about the feeding preferences of the most abundant piscivorous species found on the coasts of the studied area. Additionally, congeneric affiliation of fish introductions was not found to be an important factor explaining successful establishment of NIS. The non-indigenous toxic pufferfish, Lagocephalus sceleratus, was reported for the first time in the Mediterranean in 2003 and two years later in the coastal habitats of Rhodes. The ecological and societal impact of the pest pufferfish was investigated in coastal habitats of Rhodes. Seasonal quantitative sampling in two common coastal habitats was used to investigate habitat use of different life-stages. Sandy areas were found to be highly important for the early life stages of L. sceleratus. In contrast, Posidonia oceanica habitats were mainly preferred by larger (> 29 cm) reproductive adults with a maximum recorded size of 64 cm. Lagocephalus sceleratus was fond to be an invertebrate and fish feeder while size classification revealed a tendency for an ontogenetic diet shift with increased size to a molluscivore feeding. The ontogenetic diet shift is most probably attributed to a shift in habitat use with increasing size. During early life stages L. sceleratus inhabited sandy bottoms where it fed on various invertebrates, including the genus Nassarius and Dentaliidae. The predominant molluscan species found in the diet of larger (> 20 cm) L. sceleratus individuals was Sepia officinalis while predation of Octopus vulgaris was less successful. Sepia officinalis and O. vulgaris are of economic interest in the area and the impact of L. sceleratus on local stocks of these species is discussed. Societal impacts were also evident in the area due to increased public attention concerning the lethal effects of the toxic L. sceleratus, if consumed. Seasonal variations in the condition of L. sceleratus did not show any significance and the high conditional values together with information on high numbers caught during samplings, signifies its ability to become an important member of the coastal fish community. Combined ecological, economical and social effects clearly classify L. sceleratus a pest in the area.

Publication Type: Doctoral Theses, ISBN: 91-89677-47-1

Url: http://hdl.handle.net/2077/24869
Link: https://gupea.ub.gu.se/handle/2077/24869


Venetia Kambouroglou, 2009

Title:  Introduction of allochthonus species via ship hulls in Greek ports and consequences in local ecosystems. University of Athens.

University:  Athens University, Biology Department, Section of Zoology and Marine Biology, Panepistimiopolis 15784, Athens, Greece

Committee:  A. Nikolaidou, M. Thessalou-Legaki, A. Zenetos


Katerina Aligizaki,  2008

Title: Bionomy of Benthic Dinoflagellates in coastal areas of the North Aegean Sea with emphasis in toxic species.

University: Department of Botany, School of Biology, Aristotle University of Thessaloniki, P.O. Box 109, GR-54124 Thessaloniki, e-mail: aligiza@bio.auth.gr

Abstract: In this study, the structure and dynamics of the potentially toxic benthic dinoflagellate community in coastal, continental and island waters of North Aegean Sea is presented. The field study, which included macrophytes, sediment and water sampling, and water temperature and salinity measurements in a total of 52 sampling sites, was conducted during the period August 2003 – December 2005. In this period and until 2007, morphological identification of benthic dinoflagellates and macrophytes, abundance quantification, cultures establishment and determination of Chl-α and inorganic nutrients concentrations were carried out. Simultaneously, toxicity was investigated in dinoflagellate cells (from field and cultures) and tissues of bivalve mollusks collected from the study area.

Ten (10) potentially toxic benthic dinoflagellate species were identified, belonging to the genera Amphidinium (A. carterae and A. operculatum), Coolia (C. monotis), Ostreopsis (O. ovata and O. cf. siamensis) and Prorocentrum (P. borbonicum, P. emarginatum, P. levis, P. lima and P. rhathymum). Almost all the identified dinoflagellate species are detected in Greek coastal waters for the first time, while P. borbonicum and P. levis constitute new additions in the Mediterranean microflora. Additionally, O. ovata, O. cf. siamensis, P. rhathymum and P. emarginatum are described for the first time in the Eastern Mediterranean Sea.

The identification of the benthic dinoflagellates in the genus level did not confront any difficulty, while the opposite was arisen in the identification in species level of O. siamensis and P. lima. Some taxononical characters, such as the number and shape of valve pores, the presence or number of pyrenoids, were found unuseful. Thus, the two aforementioned taxa are referred to as O. cf. siamensis and «P. lima species complex», respectively, while the necessity for further taxonomical studies has emerged.

The highest abundance levels of Ostreopsis populations were recorded in the period between the end of summer and the beginning of autumn, while these populations were detected each year during the period July – November. This temporal pattern of Ostreopsis populations seems to be mainly related to the photoperiod changes and secondly to the temperature, as shown by the significant negative correlation between Ostreopsis populations and photoperiod changes, and the less intense positive correlation between these populations and temperature. P. lima populations were detectable all over the year, while displaying peak abundance in summer and autumn or even winter periods. The population of C. monotis and the other benthic dinoflagellates also presented highest abundance levels in summer and autumn, while, in some stations, C. monotis, P. levis and Amphidinium spp. cells were detectable in every season.

Most of the identified benthic dinoflagellates were detected in water or sediment samples only when they were simultaneously detected epiphytically. The maximum abundance levels on macrophytes reached the order of 105 and 106 cells gr-1 fwm, while, in the case of water and sediment samples, they did not exceed 104 cells L-1 and 103 cells gr-1 dws, respectively. Furthermore, it is worth noting that P. borbonicum was the only dinoflagellate species that, in some cases, was detected in sediment samples without being found epiphytically.

Regarding the macrophyte substrate, it was observed that, while in the highest abundance of Ostreopsis spp. and C. monotis firstly phaeophytes (Padina pavonica, Cystoseira sp.) and secondly phanerogams (Cymodocea nodosa) are the major contributors, the opposite was the case for P. rhathymum, P. levis and Amphidinium spp.. P. lima seemed to be able to reach high cell densities in any available substrate, despite the fact that it is clustered with Ostreopsis spp. and C. monotis.

The most abundant and widely distributed benthic dinoflagellates in North Aegean coasts were «P. lima species complex» representatives, C. monotis and Ostreopsis spp.. The negative correlations for some benthic dinoflagellates with Chl-α indicate that, mainly Ostreopsis spp., and also C. monotis and P. emarginatum, populations were favored in low Chl-α waters, rich in rhodophyte, phaeophyte and phanerogam vegetation, while they displayed minimum cell densities or are totally absent in areas, where high Chl-α concentrations were recorded, such as the western coasts of the inner part of Thermaikos Gulf.

According to the toxicity analyses conducted in the present study, Ostreopsis ovata, O. cf. siamensis, Prorocentrum lima, P. rhathymum and P. borbonicum were shown to be toxic, while C. monotis and A. carterae strains were not found toxic based on the Artemia and mouse bioassays. The haemolytic assay indicated that Ostreopsis spp. produce a toxin, analog of palytoxin (putative palytoxin, p-PLT). Palytoxin is accurately detectable with the haemolytic assay due to its characteristic to cause delayed heamolysis, which is inhibited by ouabain. Furthermore, relatively high p-PLT concentrations were detected in mussel tissues, constituting the first episode of p-PLT contamination recorded worldwide. Haemolysis assay results in cells and bivalve mollusk tissues were also confirmed by adjusted mouse bioassay protocols for PLT detection.

The phosphatase 2A inhibition assay used for Prorocentrum strains toxicity, indicated, for the first time in the Mediterranean Sea, the presence of okadaic acid and/or analogs in «P. lima species complex» strains. On the contrary, with the same assay, P. rhathymum and P. borbonicum toxicity was not associated with either okadaic acid and/or analogs production.

Based on the wide distribution and toxicity of benthic dinoflagellates in Greek coastal waters, the need for further taxonomical – phylogenetic – toxicological analyses and monitoring of these organisms and their toxins emerges.


Bardamaskos George

Title: Biological characteristics and ecological parameters influencing the distribution of the Lessepsian immigrant Siganus luridus in the Messiniakos Gulf (SE Ionian Sea).

University: University of Athens, Biology Department, Section of Zoology and Marine Biology, Panepistimiopolis 15784, Athens, Greece

Committee:  P. Megalofonou, A. Nicolaidou, P. Panayotidis

Scope: Contribution to the study of the biology (age and growth, reproduction, feeding habits, behavior, etc.), and cology (interactions with other marine biota and abiotic parameters) of the species. Determination of the reasons of its success in building large populations recently in the study area.